This type of mechanism makes it possible to indicate, upon request, the time to the closest minute, using strokes struck by two hammers on two different gongs. They can thus also make it possible to strike the hours and quarters as they pass. The hammers are actuated by lifts which are raised by a ringing mechanism. This mechanism comprises an hour rack, a quarter rack and a minute rack, provided with twelve, three and fourteen teeth, respectively, to strike the hours, quarters and minutes.
In the ringing mechanisms of the prior art, in order to adjust the movement of these racks, an hour cam is arranged on a twelve-tooth star, advancing one pitch per hour, while a quarter cam and a minute cam can be adjusted on a pivot shank. Three levers, each provided with a feeler-spindle cooperating with these cams, make it possible to determine the travel of the hour, quarter and minute racks and adjust the number of strokes struck.
Other details on this type of complication may be found, in particular on the driving force of the repeater or on the unhooking step, i.e. the triggering of the ringing mechanism, in the book “Théorie de l'horlogerie” by Reymondin et al, Fédération des Ecoles Techniques, 1998, ISBN 2-940025-10-X, pages 219 to 224.
The minute cam is thus driven at a rate of one revolution per hour and comprises four arms, one for each quarter, each arm being provided with fifteen regularly distributed stages.
It is a very difficult exercise for the watchmaker to adjust the four arms of the minute cam such that, on each of the stages, the minute ringing mechanism works correctly. Indeed, due to the complexity of a striking mechanism, in particular a minute repeater, the minute feeler-spindle has, from one piece to the next, different play or a slightly offset position, which necessarily involves, given the dimensions of the elements, individually adjusting each stage. Furthermore, from one arm to the next, the adjustment must obviously be reproduced faithfully, which is very delicate.
The aim of the present invention is to propose a ringing mechanism with easier adjustment and implementation by the horologist.